The objectives of this research are directed at characterizing lymphoid cells involving human lymphoproliferative neoplasia, particularly acute and chronic lymphocytic leukemia and lymphoma. As a model, permanent lymphoid cell lines (MOLT and RPMI 8402) derived from patients with acute lymphoblastic leukemia will be further characterized for their characteristics representing leukemic thymus-derived lymphocytes. Comparative study will be further undertaken between the T cell lines and a number of previously-established B cell lines. Fresh lymphoid cell subpopulations of normal and malignant origins will be studied in relation to those characteristics found in the cell lines. Xenoantisera specific for T-, B-cell antigens, leukemia-associated antigens and thymus-leukemia antigens will be further characterized by various immunological means, notably immunofluorescent staining. Both the cell lines and fresh lymphoid cells are to be studied with these antibody specificities. Existence of such leukemia associated antigens in lymphoid malignancies and patient's immune response to be antigens will be sought in relation to their clinical significance.